Apparatus And Methods For Purging Catheter Systems

ABSTRACT

Apparatus and methods for providing controlled pressure-flow pulses which purge a catheter system with turbulent flow flushing. Accomplishment of such controlled pressure-flow pulses is provided by a variety of inventive devices including a special plunger rod for a conventional syringe, other interactive parts for conventional syringes, an in-line catheter attachable device which automatically generates the controlled pressure-flow pulses and also single pulse, digitally operated devices.

CONTINUITY

This non-provisional United States Patent Application is acontinuation-in-part of a provisional U.S. Patent Application No.61/192,827 filed Sep. 23, 2008, titled TURBULENT FLOW SYRINGE AND FLUIDPATHWAY INSERT.

FIELD OF INVENTION

This invention is associated with apparatus and methods for clearingcatheter systems (e.g. IV lines) by creating controlled and consistentturbulent flushing pressure and flow within the system to purge the lineof unwanted residue, and, in particular, the invention is associatedwith apparatus and methods for creating such turbulent flushing pressureand flow substantially independent of clinician technique.

BACKGROUND AND RELATED ART

It is well known in IV care art that turbulent “start-stop” or“push-pause” flushing of IV catheters, e.g. central venous catheters,has become an accepted method for purging matter from catheters and,thereby, preventing build-up of deposits of blood, blood residue and IVdrugs within a catheter. Such build-up can cause partial or completeblockage of the fluid pathway in a catheter system, requiring expensiveand potentially dangerous methods for purging the catheter ornecessitating a total catheter exchange. Often, such blockages lead tointerruptions in therapy (e.g. IV therapy) that may compromise patientcare. Further, build-up of residue within a catheter can also increaseinfection risk by providing a breeding medium for microorganisms. Forthis reason, push-pause flushing is traditionally, and more or lessuniversally, taught to healthcare workers.

Push-pause (or turbulent) flushing simply requires a clinician toalternately increase and decrease an associated infusion rate duringflushing. However, efficiency and success of catheter purging usingpush-pause flushing is well known to be completely dependent uponindividual awareness, compliance and technique and a successful purgingoperation is often incomplete and problematic. For this reason, manyusers may not use such turbulent flushing effectively while others, dueto lack of knowledge or perception of value, may not use it at all.

Also, other than using turbulence for catheter clearance, syringes,pumps and other fluid forcing mechanisms associated with IV infusion aresubstantially operated in a laminar flow domain. When pulsatile flow isused, pressure and flow characteristics are constrained well below thoseturbulent and volumetric flow levels required for effective catheterpurging.

In the wide spectrum of syringe design, it is common to find art whichprovides periodic stops of various types and kinds for syringe plungers.Generally, many such stops are employed to aid in accurately measuringand dispensing a portion of a syringe fill. Once such stops are reached,it is common for the plunger to be released to thereby permit controlledand substantially laminar flow to the next stop. In other words, suchstops are generally released without a calculated, intentional force topropel the stopper with sufficient force for catheter purging. Otherstops are commonly used to limit a syringe to a single use. Generally,these stops are hard and cannot be reasonably overcome, as is common insingle-use hypodermic syringes.

An example of a plunger stop for the purpose of limiting injection offluid from a syringe is found in U.S. Pat. No. 4,642,102 issued Feb. 10,1987 to Hirofumi Ohmori (Ohmori). Ohmori discloses stops which engagerecesses in a plunger rod associated with a plunger to interruptdischarge from the syringe. After each stop, the plunger rod is strictlystopped such that no excessive force is able to drive the plunger rodfurther. Similarly U.S. Pat. No. 5,024,661 issued Jun. 18, 1991 to HarryWender (Wender) discloses a single use syringe having recesses along aplunger rod.

U.S. Pat. No. 5,318,544 issued Jun. 7, 1994 to John Drypen, et al.discloses a metering syringe having a plunger rod containing a pluralityof stop surfaces. The stop surfaces are spaced apart to define apredetermined dose volume. Plunger rod rotation relieves each stop topermit further dispensing.

U.S. Pat. No. 5,059,181 issued Oct. 22, 1991 to Robert B. Agran (Agran)also discloses a syringe assembly having recesses in a plunger rod whichare used to retard a second rearward displacement of the plunger rodassociated with a second use of the syringe assembly. In similar manner,U.S. Pat. No. 5,084,017 issued Jan. 28, 1992 to John Maffetone(Maffetone) discloses a single use syringe having a notched plunger rod.The syringe of Maffatone is taught to operate smoothly, but to dissembleitself at the completion of a single use cycle.

U.S. Pat. No. 5,280,030 issued Oct. 5, 1993 to Cesar G. Corsich, et al.(Corsich) discloses a hypodermic syringe having a blockable pistoncapable of preventing recharge and reuse under some conditions.

U.S. Pat. No. 5,328,476 issued Jul. 12, 1994 to James Bidwell (Bidwell)discloses a single-use hypodermic syringe apparatus. Ratchet grooves inan associated plunger rod are used as lock members such that whenplunger is fully inserted or reinserted into a casing, the plunger isprevented from being withdrawn relative to the casing.

U.S. Pat. No. 6,283,941 issued Sep. 4, 2001 to Joel Schoenfeld, et al.(Schoenfeld) discloses a rod-like syringe plunger having a plurality ofbead-like ratchet teeth. Schoenfeld also discloses a single use syringe.Of particular note is the statement, “It is a further object of thepresent invention to provide a single use syringe which has a smoothmechanical operation and a plunger retraction force less than theindustry maximum standard.” Such objectives are commonly held in thesyringe art for manipulating syringe plunger rods.

U.S. Pat. No. 5,891,052 issued Apr. 6, 1999 to Paul L. Simmons (Simmons)teaches a syringe plunger sabot and sabot lock disposed within a syringebody, the sabot lock mechanism being selectively movable between alocked and unlocked position. Thereby an engagement is made to create avacuum for extracting material into the syringe body.

U.S. Pat. No. 6,488,651 issued Dec. 3, 2002 to David Paul Morris et al.(Morris) discloses a mixing syringe having a plunger rod dasher whichpermits flow within the barrel for communicating material to be mixedwith material in a more proximal chamber. Other cylindrical barriersprovide within chamber defining spaces which are selectively displacedby movement of the plunger rod. Other than resistances of fluid dynamicsand friction (and stiction), no other retarding forces are taught.

U.S. Pat. No. 6,579,269 B1 issued Jun. 17, 2003 to Gennady I. Kleyman(Kleyman) discloses a dose measuring syringe. A plunger rod, as taughtin Kleyman, has formations which increase resistance to displacement ofthe plunger rod and to produce an audible sound corresponding to apredetermined volume for a measured dose. Even so, there are noteachings in Kleyman for providing momentary stops which produce apredetermined amount of turbulent flow in a catheter.

U.S. Pat. No. 5,685,864 issued Nov. 11, 1997 to Laurence M. Shanley, etal. (Shanley) discloses an aspiration syringe device which operatesoppositely to aspirate rather than discharge into a connected site. Aright angle stem of an associated plunger is equipped with spacedflanges. Interior of the syringe barrel is equipped with at least onestop. When a flange is contiguous with a stop, advancement of theplunger is prohibited. Rotation of the plunger permits furtheradvancement.

U.S. Pat. No. 4,995,869 issued Feb. 16, 1991 to Martin McCarthy(McCarthy) discloses a single-use hypodermic syringe. A syringe barrelaccording to McCarthy has an interior undulating surface over which askirt rides rearward under direction of a proximally directed manualforce. While it seems apparent that the undulations will cause apulsation in flow while discharging fluids via a patient needle, it isclear that there are no related teachings for creating turbulent flow ina catheter, a subject untouched in McCarthy.

Generally, in summary, prior art, of which art cited above is anexample, discloses and teaches plunger rod having slots, grooves andratchet teeth are for providing obstructions used for measuringpredetermined volumes of dispensed fluids or for stops associated withproviding single use syringes. Just as clinician-dependent generation ofpush-pause flow is problematic, all such art is void of teachings whichassure successful creation of turbulent flow for clearing an associatedattached catheter system. Such is the specific and precise purpose ofthe present invention.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

In brief summary, this novel invention alleviates all of the knownproblems related to generating controlled and predetermined push-pausepressures and flows thereby providing controlled and consistentturbulent flow which is effective in purging matter disposed withincatheter system. The invention comprises methods and apparatus which aredefined and designed to produce pressures resulting from dynamicreleases by predetermined forces, each for a period which provides acontrolled and consistent surge to effectively produce turbulent purgingfluid flow at a site of concern within a catheter system.

Generally, such flow is provided to a catheter system from a source offlush liquid from a container sized to hold a volume of liquidconsistent with flow volume requirements of a desired pressure pulse. Ineach case, an actuator opens a valve mechanism at a predeterminedpressure to initiate the desired liquid pulse pressure and resultingliquid flow. The sensing actuator has an operating hysteresis whichultimately stops flow to end the pressure pulse. Of course, an implementwhich, by example, may be a pump or piston, is a crucial part of theapparatus for providing sufficient pressure o activate the valvemechanism. To retain adequate pressure throughout the pulse, a memoryelement provides a source of stored energy received from the implementand releases the stored energy upon valve mechanism opening to retainthe turbulent flushing fluid pressure and flow for a desired pulseperiod.

One embodiment of the apparatus is application of the invention to asyringe, and more specifically, to a plunger rod of a syringe. In such acase, the barrel of a syringe is the container. Displacement of theplunger rod (and associated plunger) within the barrel acts as animplement to dispense liquid from the syringe. Commonly found at theproximal end of conventional syringes is a retention ring formed ofreduced diameter relative to the diameter of the rest of the syringebarrel. This retention ring is used as a tactile indicator between anentry disk disposed on the stem of a plunger rod just proximal from theplunger affixed to the plunger rod, providing an impedance which must beovercome to extract the plunger rod (and plunger) from the syringebarrel.

At least one actuating geometry, sized and shaped to require apredetermined force to displace the actuating geometry past theretention ring, is disposed proximally on the stem relative to the entrydisk. Forcing the actuating geometry past the retention ring yields theforce necessary to provide desired turbulent flushing fluid pressure andinitiate flow. Such geometry may be a disk on the plunger or aninterfacing nub on exterior edges of shafts of a plunger rod. Reflexivemotion associated with forcing the actuating disk past the retentiondisk provides the memory based, stored energy necessary to assurecontinuation of forced flow thereby providing the pressure pulse. Thelength of the pressure pulse is determined by either the plunger beingdisplaced to empty the syringe barrel or a second actuating diskdisposed proximally on the stem relative to the actuating disk justforced through the retention ring to provide a tactilely determinablestop. Note, that resistance of this stop, relative to reflexive energyapplied to displace the syringe plunger rod, provides the hysteresisspecified. In this manner, a conventional syringe barrel, in combinationwith a plunger rod made according to specifications of the instantinvention, can provide desired pulse-pause pressure pulses from asyringe substantially independent of a syringe user. It may be preferredto provide a segment of a plunger rod free of actuating geometry toprovide a “no-pulse” segment to enable conventional flush technique tocheck for possible occlusions and to verify blood return.

In another embodiment, the pulse-pause pressure pulse is provided by anin-line apparatus. Source for fluid is from a receptacle havingsufficient volume to fill a container from which the pressure pulse isgenerated, the container being a hollow cylindrical vessel whichreceives liquid from the receptacle through a one-way valve.Communication for dispensing liquid to the catheter system is throughanother one-way valve.

The valve mechanism is a plunger, sized and shaped to displace fluidwithin the vessel through the one-way valve to the catheter system.Further, the vessel has a retention ring similar to the retention ringof the barrel of a conventional syringe. A valve-actuating diskassociated with the plunger is sized and shaped to require predeterminedforce necessary to generate a desired pulse toward the catheter system.Volume of the vessel determines pulse volume. Again, as in the case ofthe syringe, reflexive action resulting from release of force when theactuating disk is driven past the retention ring assures adequate pulsepressure. The actual implement for driving the plunger is derived from abutton affixed to the plunger and associated rod whereby the plunger ismanually driven through the vessel. A spring disposed to be compressedwhen the pressure pulse is generated stores energy to return the plungerand refill the vessel for a subsequent pulse-pause cycle.

Other embodiments of the present invention involve a pressure sensitiveswitch having an actuator which opens the valve at a higherpredetermined pressure and closes at a lower predetermined pressure.Generally, the source is a fluid receptacle upstream from apressure-providing device which provides fluid dispensed at apredetermined pressure and flow. A vessel acts as a container whichcommunicates with the pressure providing device through a flowrestrictor. Further, the vessel communicates with the catheter systemthrough the pressure sensitive valve. The pressure sensitive valve isselected to have an opening pressure which provides a fluid pulse havingdesired turbulent flow characteristics and closing at a pressure after adesire flow volume has been achieved and pressure within the vessel isreduced below the lower predetermined pressure.

In one of these other embodiments, a pump provides pressure of thesource. A spring loaded piston chamber provides opportunity to gathervolume for the pressure pulse which fills at a pressure lower than thehigher predetermined pressure through a flow restrictor affixed to theoutput of the pump, but at a pressure higher than the lowerpredetermined pressure. Thus, the higher predetermined pressure isreached only upon filling the chamber. Once the chamber is filled, thevalve is opened by the actuator to initiate the controlled pressurepulse. When the chamber is emptied, pressure in the vessel drops belowthe lower predetermined pressure and the actuator closes the valve. Ifthis embodiment remains affixed to the catheter system a subsequentpressure pulse is generated automatically.

Another of other embodiments involves a squeezable tube. In this casethe tube communicates with the catheter system through a pressuresensitive valve, having valve actuator opening characteristics asdisclosed supra. Upstream the tube communicates with the source througha one-way valve. Pressure from the source does not reach or exceed thehigher predetermined pressure, but is sufficient to fill the tube. Thus,pressure from the upstream source and elastic memory in the tube causethe tube to fill through the upstream one-way valve. Once the tube isadequately filled, it is selectively squeezed to cause the pressure torise to at least the higher predetermined pressure. Once pressure withinthe tube is at or above the higher predetermined pressure, the valve isopened and the pressure pulse is initiated. The pressure pulse iscontinued by reflexive action following valve opening. Expulsion ofliquid from the tube ultimately results in valve closing ending thepressure pulse. The pressure pulse may be continued until the tube issubstantially empty.

Methods for using embodiments of the instant invention generally involvefilling a chamber or vessel, of predetermined size, from which a pulseof liquid is to be dispensed, causing pressure within the chamber orvessel to exceed a predetermined pressure and selectively opening apathway to the catheter system only when that pressure is achieved. Inthat manner, a desired, controlled pulse-pause pressure pulse isachieved and provided substantially independent of performance of auser.

Accordingly, it is a primary object to provide apparatus which providessubstantially user independent, controlled pulse-pause pulsatile flow ofsufficiently turbulent flushing pressure and flow within a cathetersystem to substantially purge the line of unwanted residue.

It is a primary object to provide such apparatus which is used within abarrel of a conventional syringe.

It is another primary object to provide such apparatus which providesin-line operation between a fluid source and the catheter system.

It is an object to provide such apparatus which provides for a series ofmanually generated pulse-pause pressure pulses.

It is an important object to provide such apparatus which uses a pump asan implement.

It is another object to provide apparatus which provide controlledpressure pulses resulting from opening and closing a pressure sensitivevalve.

These and other objects and features of the present invention will beapparent from the detailed description taken with reference toaccompanying drawings.

DEFINITIONS OF SOME TERMS USED IN THE SPECIFICATION

-   catheter system\n: a combination of tubes and other devices used to    deliver fluids to patients, e.g. a medical catheter (e.g. IV    catheter), delivery tubing (e.g. feeding tube) and associated    connectors-   fluid\n: a gas or liquid-   IV\adj: a mode of delivery of fluids to a patient, in this case the    mode is Intravascular-   laminar flow\n: streamline flow which is relatively smooth and even,    such as flow near a solid boundary and contrasted with turbulent    flow-   turbulent flow\n: a fluid flow in which the velocity at a given    point varies erratically in magnitude and direction with time and is    thus essentially variable in pattern and is contrasted with laminar    flow-   valve mechanism\n a fluid control device generally defined herein to    be a device for initiating a pressure pulse when opened and ending    the pressure pulse when closed; within this general definition,    pulse-pressure generating action of a syringe plunger rod being    displaced to actuate a pressure pulse is considered to be a valve    mechanism

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of a syringe and plunger rod made according tothe present invention where stem of the plunger rod has a plurality ofdisks disposed upon the length thereof.

FIG. 2 is a cross section of the syringe and plunger rod and seen inFIG. 1.

FIG. 2A is a cross section of a syringe and plunger rod which is similarto the syringe and plunger rod of FIG. 2, but wherein edges of disks areshaped to facilitate displacing the plunger rod into the syringe anddeterring the plunger rod from being removed from the barrel, once sodisplaced.

FIG. 2B is a cross section of a syringe and plunger rod which is similarto the syringe and plunger rod of FIG. 2, but wherein edges of disks areshaped to facilitate displacing the plunger rod out of the syringe oncedisplaced therein.

FIG. 2C is a cross section of a syringe and plunger rod which is similarto syringes and plunger rods of FIGS. 2, 2A and 2B, but having nubsalong a shaft of a plunger rod instead of disks.

FIG. 3 is a perspective of the plunger rod seen in FIG. 1.

FIG. 4 is a perspective of a syringe and plunger rod wherein the plungerrod is similar to the plunger rod of FIG. 1 but fabricated with aplurality of breakaway rings disposed about to stem of the plunger rod.

FIG. 5 is a perspective of the plunger rod seen in FIG. 4.

FIG. 6 is a perspective of the syringe and plunger rod seen in FIG. 4with at least one breakaway ring sheered from the stem of the plungerrod.

FIG. 7 is a perspective of a syringe and plunger rod wherein the plungerrod is similar to the plunger rod of FIG. 1 but having a pattern ofundulations on the stem and a constraining elastomeric ring about theproximal syringe barrel opening.

FIG. 8 is a cross section of the syringe, plunger rod and elastomericring seen in FIG. 7.

FIG. 9 is a perspective of an automatic, in-line pulsing device madeaccording to the present invention.

FIG. 10 is a cross section of the automatic, in-line pulsing device seenin FIG. 9 showing state of the device at the end of a pulse.

FIG. 11 is a cross section of the automatic pulsing device seen in FIG.9 showing state of the device when charged before actuating a pulse.

FIG. 12 is a cross section of the automatic pulsing device seen in FIG.9 showing state of the device during pulse generation.

FIG. 13 is a perspective of the device seen in FIG. 9 with a syringeaffixed to the device to provide a fluid pressure source.

FIG. 14 is a schematic drawing of a system which employs a pumped fluidsource for the device seen in FIG. 9.

FIG. 15 is a perspective of a squeezable device for providing acontrolled pressure pulse according to the instant invention.

FIG. 16 is a cross section of the device seen in FIG. 15.

FIG. 17 is a cross section of the device seen in FIG. 14 with a medicalsection squeezed at the end of a controlled release pressure pulse.

FIG. 18 is a perspective of a manually operated controlled pressurepulse device according to the present invention.

FIG. 19 is a cross section of the device seen in FIG. 18 filled beforeinitiating a controlled pressure pulse.

FIG. 20 is a cross section of the device seen in FIG. 18 at the end of apressure pulse.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In this description, the term proximal is used to indicate the segmentof the device normally closest to the object of the sentence describingits position. The term distal refers to a site opposite the proximalsection. Reference is now made to the embodiments illustrated in FIGS.1-20 wherein like numerals are used to designate like parts throughout.

Reference is now made to FIG. 1 wherein a preferred embodiment of asyringe/plunger rod combination 10 of the instant invention is seen.Combination 10 comprises a conventional syringe barrel 20 and a plungerrod 30. Salient features of combination 10 are better seen in FIG. 2 tocomprise barrel 20 having a retention ring 40 disposed at proximalbarrel hole opening 42 and plunger rod 30 comprising a plurality ofactuating geometry, interfaces or rings, generally numbered 50) disposedalong a stem 60 thereof. In addition, as is common with plunger rods ofconventional syringes, plunger rod 30 has a plunger 70 affixed to thedistal end 80 of stem 60. It may be noted that distal end 80 has athreaded geometry portion 90 which permits plunger rod 30 to be affixedto plunger 70 after barrel 20 is tilled with liquid, generallyreferenced as liquid 72. A plunger rod 30 is seen alone in FIG. 3providing a clearer view of threaded portion 90.

Further, plunger rod 30 has a first ring 92 which can be forced pastretention ring 40 when plunger 70 and stern 60 are inserted into barrel20. First ring 92 is sized and shaped to be forcible displaced throughretention ring 40, but provide a tactilely discernable stop such thatplunger 70 is not inadvertently displaced out of barrel 20.

Each actuator ring 50 is sized and shaped to be obstructed by retentionring 40. Each actuator ring 50 is further sized and shaped to require apredetermined force which must be exceeded to displace a contactingactuator geometry (e.g. retention ring interface 50) past retention ring40. For this reason, fluid within barrel 20 is displaced with resultingacceleration and velocity resulting from the predetermined force whenthe contacting ring 50 is releasibly displaced through retention ring40. Generally the resulting acceleration and velocity is of liquid whichis discharged from syringe barrel 20 to turbulently flush liquid 72through an associated catheter system. In this manner, each time acontacting ring 50 is displaced past retention ring 40 a pulse ofpressurized liquid 72 is purged into the catheter system providing aturbulent flushing pulse of liquid 72 there through.

As well, a more proximal ring 94 of rings 50 may be further shaped andsized to require a force which is greater than more distal rings 50 toprovide a reminder that the pulse resulting from actuation using ring 94is the last pulse provided by liquid 72 from combination 10. For thisreason, ring 94 may be referenced as reminder ring 94 hereafter. Note,that, if plunger rod 30 is not displaced sufficiently far into barrel 20to displace reminder ring 94 past retention ring 40, no back flow orreflux should occur in an associated catheter system. Note that proximalend 98 of stem 60 is convex or dome shaped to facilitate application ofdigital force against plunger rod 30.

As well, it may be noted that rings 50 are not necessarily spaceduniformly. As an example a space 99 between first ring 92 and next mostproximal ring 50 is relatively large compared to space between otherrings, generally numbered 50. This provides for a “no-pulse” segmentwhich may be used for conventional sampling for catheter blood flow toassure proper catheter operation.

Attention is now directed to FIG. 2A wherein a second combination 20′ ofa conventional syringe barrel 20 and a plunger rod 30′ is seen. Plungerrod 30′ is similar to plunger rod 30, having a series of actuator rings50′ disposed along the length thereof. However, in the case ofcombination 10′, rings 50′ are shaped and sized (as seen in FIG. 2A) tobe more easily displaced into barrel 20 (and distally through retentionring 40) than displaced barrel 20 (proximally through retention ring).Such meets a condition whereby plunger rod 30′ is not easily removedfrom barrel 20, once used to promote a single use application.

On the other hand, it may be desired to refill and reuse such acombination. In such a case, it is desired to displace a plunger rod 30″of a third combination 10″ more easily proximally than distally. In sucha case, actuating rings 50″ disposed along a stem 60 are shaped as seenin FIG. 2B.

Rings 50 seen in FIG. 2, may be replaced by nubs 52 on a plunger rod 32as seen as combination 12 in FIG. 2C. Replacement of rings 50 by nubs 52may be done without degradation of effect of producing desiredturbulence by sizing and shaping nubs 52 to require forces similar tothat required of rings 50 for displacement past retention ring 40.

Another embodiment, seen as combination 110, of the instant invention isseen in FIGS. 4-6. As in combination 10, combination 110 comprises aconventional syringe barrel 20. Note that syringe barrel 20 has aproximal entry hole 122 associated with retention ring 40. As seen inFIGS. 4 and 5, an associated plunger rod 30 also comprises a series ofactuator rings, generally numbered 150, disposed along a stem 60 ofplunger rod 130. However, rather than being sized and shaped to beforced through retention ring 40 of barrel 20 to create a desiredpressure pulse, rings 150 are affixed to stem 60 in a manner whichpermits each actuation ring 150 to be sheared from stem 60 as it isdisplaced into barrel entry hole 42.

Shear force at separate actuation rings 150 from stem 60, similar todisplacement force past retention ring 40 of combination 10, isgeometrically and mechanically designed to provide a predeterminedacceleration and velocity which purveys desired turbulent flow to purgeand discharge unwanted contaminants from a downstream catheter system.Note, in FIG. 6, that a first more distally disposed actuator ring 150is seen to be captured by a second, more proximally disposed actuatorring 150 exterior to hole in FIG. 6. Note that piling up of shearedactuation rings 150 may be used to prevent a syringe from being fullyevacuated.

Yet another embodiment of the instant invention is seen as combination210, which may use a conventional syringe barrel 20, is seen in FIGS. 7and 8. In addition to barrel 20, combination 210 comprises anelastomeric restrictor 230 a plunger rod 240 with a stem 242. Stem 242comprises a plurality of elongated side members, each numbered 244. Eachside member has an undulating exterior edge, numbered 246. High pointsof the undulations are generally numbered 248.

Restrictor 230 is shaped and configured to provide a port about barrelentry hole 42 (see FIGS. 1 and 2). A restrictor entry hole 250 is sizedand shaped to obstruct inward displacement of plunger rod 240 uponcollision between restrictor 230 and each high point 248. A combinationof selected durometer of the elastomer of restrictor 230, and collisiongeometry of high points 248 and hole 250 combine to require apredetermined force for further displacement of plunger rod 240. Thispredetermined force is comparable to the force required for displacementof plunger rod 30 past retention ring 40 (see FIGS. 1-3). In thismanner, a pressure pulse which provides turbulent flow for purging anattached catheter system is generated each time high points 248 aredisplaced through hole 250 of restrictor 230.

Reference is now made to FIGS. 9-12 wherein an in-line automatic pulsingdevice 310 made according to the instant invention is seen. As seen in.FIG. 9, device 310 comprises an upstream or proximal connection 320,into which liquid from a liquid source is provided. Further device 310comprises an output port and connector 330 which may be connected to adownstream catheter system. For proper operation, liquid pressureavailable from the source must be greater than desired pressure of apurging liquid pulse emitted by device 310.

As seen in FIG. 10, a pressure sensitive valve 340 is disposed to closeoutput port and connector 330 when pressure is below the desiredpressure. Just distal from proximal connection 320 is a check valve 350to obstruct backflow and retard inflow to a predetermined level of flow.Medially disposed between pressure sensitive valve 340 and check valve350 is a pulse reservoir chamber 360. Disposed within chamber 360 is apiston 370 and spring 380 which acts within chamber 360 to store avolume of liquid when valve 330 is closed.

When choosing pressure sensitive valve 340, a valve should be selectedwhich has an opening pressure to closing pressure hysteresis having apredetermined pressure differential for purposes clarified hereafter.The pressure differential being defined as a difference between releasehigh pressure and a low closing pressure. The high pressure being apressure which creates a pressure pulse having sufficient force and flowto cause down stream turbulence which purges a desired amount ofmaterial from an attached catheter system. The lower pressure being apressure to which pressure inside device 310 falls after clearing ofliquid from chamber 360. Note that, for pressure inside 310 to fall tothe lower pressure, inflow from the source must be restricted to a lowerflow rate than outflow through output port and connector 330.

Steps of operation of device 310 are seen to embody a beginning stateseen in FIG. 10 where chamber 360 is empty and spring 380 isdecompressed and valve 350 is closed. Subsequent filling of chamber 360is seen in FIG. 11. Valve 340 is opened when spring 380 is fullycompressed to discharge liquid from device 310 thereby. Of course, oncevalve 350 closes, the pulse cycle repeats.

Sources for pressurized fluid for device 310 are seen in FIGS. 13 and14. In FIG. 13, a conventional syringe 390 is affixed to proximalconnection 320. Source pressure is provided by the force displacing anassociated plunger rod 392. Note that sufficient pressure is required tofully charge chamber 360 before actuating valve 350.

In FIG. 14, a more sophisticated pressure providing source system isseen including a saline bag 304, a pump 396 and a variable liquid flowrestrictor 398. Source liquid from bag 394 is drawn and pumped by pump396 to provide pressure equal to or greater than the high pressurenecessary to open valve 350. Variable restrictor is set to determinepump 396 to device 310 liquid transfer rate to determine device 310output pulse rate.

Reference is now made to FIGS. 15-17 wherein an in-line pinch or squeezepump 410, made according to the instant invention, is seen. As seen inFIG. 16, device 410 comprises an upstream or proximal connection 420,into which liquid from a liquid source is provided. Further device 410comprises an output port and connector 430 which may be connected to adownstream catheter system. For proper operation, liquid pressureavailable from the source must only be greater than filling pressure ofan expandable tube 440 which is sized and shaped to be easily filled andpurged by squeezing.

As seen in FIG. 16, a pressure sensitive valve 340 (see also FIGS. 11-13of device 310, disclosed supra) is disposed to close output port andconnector 430 when pressure is below a predetermined pressure. Justdistal from proximal connection 420 is a check valve 450 to obstructbackflow. Tube 440 provides a storage medium which defines pulse flowquantity when device 410 is actuated. To operate, tube 440 is squeezeduntil valve 340 is opened to provide a pressure pulse according to thepresent invention. Continued reflexive squeezing dispenses liquidthrough valve 340 to create a pulsatile flow of liquid having sufficientturbulent flow and pressure to purge an attached catheter system. Notethat pressure of source liquid need only be at a sufficiently highpressure to fill tube 440 and that tube 440 may have sufficient inherentstructural memory to provide a somewhat negative filling pressurerequirement. This same memory reduces liquid pressure inside tube 440 tocause valve 340 to close at the end of a pulse generating cycle.

Another device 510 which provides manually, digitally generatedcontrolled pressure pulses for purging catheter systems according to thepresent invention is seen in FIGS. 18-20. As seen in FIG. 19, device 510comprises an upstream or proximal connection 520, into which liquid froma liquid source is provided. Further device 510 comprises an output portand connector 530 which may be connected to a downstream cathetersystem. For proper operation, liquid pressure available from the sourcemust only be greater than filling pressure of a spring pistoncombination 540. Combination 540 comprises a depressible button and rod550, a compressible spring 560 and a plunger 570. Plunger 570 is sizedand shaped to evacuate liquid m a hollow vertical chamber 580 whichcommunicates orthogonally with a hollow liquid flow chamber 590 disposedfor liquid communication between proximal connection 520 and output port530. Amount of liquid stored in vertical chamber 580 and released upondisplacement of plunger 570 determines pulse volume of liquid deliveredto the downstream catheter system.

As seen in FIG. 19, a pressure sensitive valve 340 (see also FIGS. 11-13of device 310, disclosed supra) is disposed to close output port andconnector 530 when pressure is below a predetermined pressure. Justdistal from proximal connection 520 is a check valve 450 to obstructbackflow. To operate device 510, button 550 is depressed to open valve340 thereby providing a pressure pulse according to the presentinvention. Continued reflexively depressing button 550 dispenses liquidthrough valve 340 to create a pulsatile flow of liquid having sufficientturbulent flow and pressure to purge an attached catheter system. Notethat pressure of source liquid need only be at a sufficiently highpressure to fill chamber 580 and that combination 540 with spring 560should have sufficient inherent structural memory to provide a negativefilling pressure inside chamber 590. This same memory reduces liquidpressure inside chamber 590 to cause valve 340 to close at the end of apulse generating cycle.

To operate device 510, chamber 580 is permitted to fill with liquidprovided through connector 520. Button 550 is depressed to providesufficient force to open valve 340 and reflexively thereafter continuedto be depressed until liquid is purged from chamber 580 as seen in FIG.20 to produce the desired purging pressure pulse. Once combination 540is fully depressed, force on button 550 is relieved to permit refillingof chamber 580 for generating a subsequent pressure pulse.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is: 1-12.(canceled)
 13. A plunger rod, which in combination with an attachedplunger of a syringe, is used to displace liquid within a syringe barrelwhich has a proximally disposed retention ring which providesopportunity for a tactile indication of a discernable stop to indicate alimit of proximal displacement of the plunger and plunger rod within thebarrel, said plunger rod comprising: an elongated stem disposed betweensaid plunger and a proximal end of the stem; an entry disk proximallydisposed relative to the plunger on said stem for interacting with theretention ring; plurality of actuating geometry disposed along the stem,the plurality of actuating geometry obstructed by the retention ringsuch that displacement of the plurality of actuating geometry past theretention ring creates acceleration and velocity within the syringebarrel; and a reminder ring proximal to the plurality of actuatinggeometry which is sized and shaped to require a force to move thereminder ring past the retention ring which is greater than a forcerequired to move the plurality of actuating geometry past the retentionring, providing a tactile indication that the acceleration and velocitywithin the syringe barrel resulting from actuation using the reminderring is a last acceleration and velocity created within the syringebarrel.
 14. A flush syringe comprising: a barrel including a proximalopening and a retention ring disposed at the proximal opening; and aplunger rod disposed within the barrel for slideable displacement withinthe barrel, the plunger rod comprising a stem and plurality of actuatinggeometry disposed along the stem, the plurality of actuating geometryobstructed by the retention ring such that displacement of the pluralityof actuating geometry past the retention ring creates acceleration andvelocity within the barrel, and a reminder ring proximal to theplurality of actuating geometry which is sized and shaped to require aforce to move the reminder ring past the retention ring which is greaterthan a force required to move the plurality of actuating geometry pastthe retention ring, providing a tactile indication that the accelerationand velocity within the barrel is a last acceleration and velocitycreated within the barrel.
 15. The flush syringe of claim 14, whereinthe stem of the plunger rod comprises a space between the plurality ofactuating geometry that prevents acceleration and velocity within thebarrel as the plunger rod is displaced distally within the barrel. 16.The flush syringe of claim 14, wherein the plurality of actuatinggeometry comprises a plurality of rings.
 17. The flush syringe of claim16, wherein the plurality of rings are shaped and sized to be moreeasily displaced distally through the retention ring than displacedproximally through the retention ring.
 18. The flush syringe of claim16, wherein the plurality of rings are shaped and sized to be moreeasily displaced proximally through the retention ring than displaceddistally through the retention ring.
 19. The flush syringe of claim 14,wherein the plurality of actuating geometry comprises a plurality ofnubs.
 20. The flush syringe of claim 16, wherein the plurality of ringscomprise shearable-rings that are sheared from the stem as the plungerrod is displaced into the barrel.
 21. The flush syringe of claim 20,wherein the sheared plurality of rings pile up at the retention ring andprevent full evacuation of the barrel.
 22. The flush syringe of claim13, wherein the barrel comprises an amount of liquid and the restrictorcomprises an elastomer having a selected durometer that providesturbulent flow to the liquid when the high points are displaced throughthe restrictor entry.
 23. The plunger rod of claim 13, wherein theplurality of actuating geometry comprises a plurality of rings.
 24. Theplunger rod of claim 23, wherein the plurality of rings compriseshearable-rings that are sheared from the stem as the plunger rod isdisplaced into the syringe barrel.
 25. The flush syringe of claim 13,wherein the plurality of actuating geometry comprises a plurality ofnubs.